Ionization fire alarm system



Feb. 15, 1966 P. A. MAD R IONIZATION FIRE ALARM SYSTEM 3 Sheets-Sheet 1 Filed 001;. 30, 1961 mwi Maw 14% M 1 47W Feb. 15, 1966 P. A. MA ER 8 IONIZATION FIRE ALARM SYSTEM Filed Oct. 30, 1961 3 Sheets-Sheet 2 Fig. 2

ANODE 27 77 72 '32 37 30 26 25 I SPRING 22 Fig. 6

i Feb. 15, 1966 P. A. MADER 3,235,858. IONIZATION FIRE ALARM SYSTEM Filed Oct. 30, 1961 3 Sheets-Sheet 5 Fig. 5

United States Patent 3,235,858 IONIZATION FIRE ALARM SYSTEM Paul A. Mailer, Zollikofen, Bern, Switzerland, assignor to Seeuriton A.G., Zollikofen, Bern, Switzerland Filed Oct. 30, 1961, Ser. No. 148,674 Claims priority, application Switzerland, Nov. 2, 1960,

3 Claims. (c1. 340 214 The present invention relates to an ionization fire alarm system of the type having a plurality of fire detecting units each provided with a closed ionization chamber series connected with an open ionization chamber, the ionization of which is variable in response to combustion gases for giving the alarm by means of a relay tube.

Such fire alarm systems have the disadvantage that dangerous and abnormal increases of temperature, such as for instance provoked by electric heating or by the combustion of alcohol and illuminating gas, which may lead to a fire when acting on inflammable substances during a certain period of time, cannot be detected by the mentioned type of fire alarm systems. Moreover, the readiness of operation only may be tested at the place where the fire alarm system is installed, by means of smoke or gases specially produced for this purpose, by means of auxiliary equipment.

It is an object of the present invention to avoid these disadvantages. The fire alarm system according to the invention comprises temperature limiting means associated with each fire detecting unit and operating in response to a predetermined limit temperature independently of the presence of combustion gases, electric ion means associated with the open ionization chamber for checking the readiness of operation of the fire detecting unit and calibrated indicator means for indicating the conditions of operation of the fire alarm system, the lightingup of the tube of a fire detector unit being visible from the exterior for visibly indicating the condition of operation of each fire detecting unit.

Further, known ionization fire alarm systems do not have an aesthetically satisfying shape and present ditficulties with respect to mounting and interchangeability of the parts, inasmuch as the used tubes, for example, are of a special design or deviate from the usual, commercial executions and are therefore not easily inter changeable.

According to a further feature of the invention, in an ionization fire alarm system or smoke detector of the type referred to, the open ionization chamber, the closed ionization chamber and the triode tube mounted in a tube socket are arranged coaxially one behind the other in a tube-shaped housing having on its front surfaces terminal contacts. Such an ionization smoke detector may easily be placed at an appropriate location on account of its tubelike shape. It may be easily mounted in sockets, in a manner similar to gas discharge tubes, and is of an aesthetically satisfying shape. Moreover, the triode tube may easily be exchanged.

The novel features of the invention, together with further objects and advantages, will become apparent from the several embodiments thereof shown in the accompanying drawings and described in the following specification.

-In the drawings:

FIGURE 1 shows a block diagram of a fire alarm system according to the invention.

FIGURE 2 is a diagrammatic longitudinal section of an ionization fire detecting unit.

FIGURE 3 is a fragmentary sectional view of FIG- URE 2 at an increased scale.

FIGURE 4 is a view of a fire detecting unit mounted in a recess in the ceiling.

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FIGURE 5 is a view of a fire detecting unit in a suspended execution, and

FIGURE 6 is a block diagram of the low voltage sup- :ply of the fire alarm system.

With reference to FIGURE 1 of the drawings, a group of n fire detector units M M M are connected with a central station Z by means of a three-wire line L L and L The fire detecting unit M has an open ionization chamber K and a series connected ionization chamber K and an ionization tube R6 which, upon ignition, provides an optical indication which is visible from the exterior. A temperature limiting device TG is provided the contact path tg of which is closed by the action of a spring when a melting lead is fused. In the open ionization chamber K there is a grid SG connected by means of a lead L with a test key PT.

R is an anode resistor of the triode tube R6 and R is a limiting resistor associated with the temperature limiting device TG The other fire detecting units M M are similarly constituted as the fire detecting unit M In the represented state of operation, i.e. under normal conditions the test lead L is connected through the test key PT with a negative lead L and the circuit is closed through an end resistor R,,, U being the operating voltage applied to the lead L An indicating apparatus A at the central stat-ion controls the different states of operation, such as readiness of operation, loop interruption, readiness of functioning and alarm. The further equipment of the alarm central station is of normal conventional kind and therefore is not represented and de scribed.

When the test key PT is switched over, the grid of the open ionization chambers K of all fire detecting units M are supplied through the test lead L with a positive voltage U corresponding to the degree of ioni zation in the chamber K in case of an alarm, thus producing a decrease of the current in the chamber K whereby the ionization voltage U] is increased to such a degree that all triode tubes R6 become conductive and are ignited. Thus, it is possible to check the readiness of functioning of all fire detecting units grouped together from a central station Z by means of the suitably calibrated indicating apparatus measuring the current flow in the anode lead L which signalizes any nonresponding detecting unit M. It is possible to find out the different defective detecting units M by means of the optical indication Li directly depending on the ignition condition of the relay tube.

The open ionization chamber responds in case of an alarm, as already mentioned, only to the presence of combustion gases, but not to abnormal increases of temperature. In order to obtain a response to such increases of temperature, a temperature limiting element TG is provided which beings to melt when a predetermined temperature is reached. Thus, a contact path zg is closed by the action of the spring, and the grid of the triode tube is connected with the anode voltage U through the limit resistor. Thereby the tube is ignited and, as already mentioned, the alarm is given.

An electrode of the open ionization chamber formed by a melting lead could also be used as temperature limiting element.

The detector unit shown in FIGURE 2 comprises an armature 1 having two tube sockets Z, 3 into which the end walls 4, 5 of a tube-shaped housing 6 of the unit may be interchangeably inserted by means of terminal pins 7, 8 and 9, 10, respectively, in the manner of a turning lock used for mounting gas discharge tubes. A safety pin 11 provided on the tube base enters a segment-like slot 12 on the end Wall 4 making possible a fool-proof insertion of the housing 6. This housing 6 simultaneously forms the cathode of an open ionization chamber 13, whereas the associated anode 14 is disposed centrally in the ionization chamber 13 and a grid 15 is placed within the housing 6. A ring 16 is placed in the grid 15 in a median plane perpendicular to the axis of the open ionization chamber 13. The two opposite sides of the ring 16 each carry a radiation source 17 and 18, respectively, such as a radium preparation (FIGURE 3). Moreover, the ring 16 carries two shutter rings 19, 20 made of metal wire, the diameter of which can be varied at will in order to partially screen the alpha radiation of the radiation sources 17, 18 and to reduce more or less the ionization intensity in the open ionization chamber 13. As shown, the alpha radiation of the sources 17, 18 is directed on both sides of the ring 16 along the housing 6 and parallel to the central anode 14. Thus, on the one hand the length of the elfective ionizable path of the alpha radiation in the chamber 13 is doubled, and on the other hand the maintenance of a sufficiently great neutral recombination zone on the narrowest diameter in the chamber 13 is ensured. A cylindrical melting lead element 21 having an adjustable melting temperature and being extended upon melting by the action of a compression spring 22 to the right hand extremity of the anode 14, is inserted in the anode 14 in the middle of the chamber 13. When such an extension takes place, the right hand extremity of the anode 14 engages a contact plate 23 connected with the terminal pin 9 which in turn is connected with the positive supply voltage at the terminal pin 7.

A closed comparison chamber 24 having a sleeve-like cathode 25 connected with the anode 14 of the open chamber 13 is arranged coaxially with the open ionization chamber 13. A radiation source 26 is disposed on the inner surface of the cathode 25, and an anode 27 having the form of a helix is placed centrally. This closed ionization chamber 24 is fixed to one side of a highly insulating tube base 28 interchangeably receiving the cathodic triode tube 29. As shown, the cathode 36 of the tube 29 is connected with the housing 6 forming the cathode of the open ionization chamber 13, the grid 31 of the tube 29 is connected with the cathode 25 of the closed ionization chamber 24, and the anode 32 of the tube 32 is connected with the terminal pin 7 supplied with the positive mains voltage, whereas the negative mains voltage is connected through the terminal pin 8 with the housing 6. The housing 6 is provided with slots 33 (FIGURES 4 and within the limits of the open ionization chamber 13 and the tube 29. If the open ionization chamber 13 contains the normal atmospheric air the potential of the anode 14 and of the cathode 25 of the closed ionization chamber 24 connected with the anode 14 and the potential of the grid 31 of the tube 29, respectively, are so low that the tube is not ignited. If combustion gases are entering the chamber 13 the ionization present in this chamber 13 is so changed that the voltage at the anode 14 and at the cathode 25, and the grid 31 of the relay tube 29 is increased and that the relay tube 29 is ignited and triggers the alarm.

Moreover, if a positive grid potential is applied to the grid through the terminal pin 10 the ionization current decreases. Thus, the voltage at the anode 14 and at the cathode 25, and the grid 31 of the tube 29 increases. It is obvious that the sensibility of the alarm unit may be increased by increasing this voltage at the grid, whereby the tube 29 ignites earlier and the alarm is sooner given when combustion gases are entering. The grid voltage may be increased to such a degree that it already causes the tube 29 to ignite Without any combustion gases being present. This fact may be used for testing the correct operation of the alarm detecting unit.

With an increase of temperature the melting lead element 21 becomes operative independently of the presence of combustion gases, When it melts, the right hand end of the ano e 14 is broug t into contact with the contact plate 23 by the action of the spring 22. Thus, the positive supply voltage is applied from the terminal pin 9 to the anode 14, to the cathode 25 and to the grid 31 of the tube, thus causing the tube to ignite and the alarm to be glven.

According to FIGURE 4 the tube-shaped housing 6 having slots 33 is mounted in an armature 1 having tube sockets 2, 3. The armature is fixed in a wooden box 34"- mounted in a recess in the ceiling to be flush with the face thereof. The wooden box 34 is covered by a front plate 35 in such manner that only about two thirds of the housing 6 project below the ceiling. I

As shown in FIGURE 5, the tube-shaped housing 6,.

also having slots 33, is provided at one end with a cover. cap 37. Around the periphery of the housing 6 the orna-- mental wings 38 are angularly spaced at equal distances. The electric current supply lead may be extended through these ornamental wings 38 from the suspension head 36 to the cover cap 37, and the ornamental Wings are simultaneously used for conducting the air uniformly through the slots 33 of the housing 6. As shown, the fire detecting unit is suspended by the suspension head 36 in a vertical position.

The block diagram according to FIGURE 6 shows how an ionization fire detecting unit having a closed ionization chamber K an open ionization chamber K and a tube R6 may be operated at low voltage. The low voltage mains L L are connected with the primary winding of a transformed T if necessary, through a transistorized inverted converter or vibrator. The vibrator only is provided, if the low voltage is a direct current voltage. The secondary winding of the transformer is connected with the fire detecting unit through a rectifier G resistors R and R and a condenser C, and supplies the required operation voltage. The lead L supplies the required grid voltage for the grid of the open ionization chamber K I claim:

1. An ionization fire alarm system having a plurality of fire detecting units, each including a closed ionization. chamber series-connected with an open ionization cham-- her, the air ionization thereof being variable in response to the action of combustion gases to release an alarm signal in an indicator of a central post by means of a triode tube, said system comprising a grid electrode arranged in the open ionization chamber of each fire detecting unit for checking the operational readiness of the unit, said grid electrode being connectable to a testing voltage to indicate the condition of operations of the group of detecting units on the indicator at the central post, whereby, in case of alarm, the condition of operation of each fire detecting unit is visible when the grid electrode lights 2. A fire alarm system as claimed in claim 1 in which the grid electrode in each open tubular ionization chamber has the form of a coaxial tubular electrode and is connectable to a positive grid potential for adjusting the sensitivity of the fire detecting unit.

3. A fire alarm system as claimed in claim 1 comprising temperature responsive means arranged between the grid and the anode of the triode tube and operating in response to a predetermined temperature independently of the presence of combustion gases, in which said temperature responsive means are constituted by an electrode of the open ionization chamber.

4. A fire alarm system as claimed in claim 1, in which the open ionization chamber, the closed ionization chamber and the triode tube inserted into a tube socket are placed coaxially one behind the other in a tubular housing having contact means at its end faces.

5. A fire alarm system as claimed in claim 4, in which a ring having a radiation source at each of the two opposite ring faces, is arranged coaxially in the median transverse plane of the cylindrical open ionization cham ber.

6. A fire alarm system as claimed in claim 5, in which a shutter ring is associated With each radiation source for adjusting the radiation intensity.

7. Fire alarm system according to claim 4, in which turning locks are provided on each end face of said housing and are arranged for introducing the housing positively in correct position into its armature sockets.

8. Fire alarm system according to claim 4, in which one of the end faces of the housing forms a suspension head and the other end face forms a cover cap permitting the suspension of the housing in a vertical position, ornamental wings being provided on the periphery of the housing and supply leads extending from the cover cap to the suspension head, within said Wings.

References Cited by the Examiner UNITED STATES PATENTS 2,145,866 2/1939 Failla 340-237 2,621,239 12/1952 Cade et al 340- 227 3,056,123 9/1962 Shamos 340--237 FOREIGN PATENTS 398,722 9/1933 Great Britain. 831,812 3/1960 Great Britain.

NEI'L C. READ, Primary Examiner. 

1. AN IONIZATION FIRE ALARM SYSTEM HAVING A PLURALITY OF FIRE DETECTING UNITS, EACH INCLUDING A CLOSED IONIZATION CHAMBER SERIES-CONNECTED WITH AN OPEN IONIZATION CHAMBER, THE AIR IONIZATION THEREOF BEING VARIABLE IN RESPONSE TO THE ACTION OF COMBUSTION GASES TO RELEASE AN ALARM SIGNAL IN AN INDICATOR OF A CENTRAL POST BY MEANS OF A TRIODE TUBE, SAID SYSTEM COMPRISING A GRID ELECTRODE ARRANGED IN THE OPEN IONIZATION CHAMBER OF EACH FIRE DETECTING UNIT FOR CHECKING THE OPERATIONAL READINESS OF THE UNIT, SAID GRID ELECTRODE BEING CONNECTABLE TO A TESTING VOLTAGE TO INDICATE THE CONDITION OF OPERATIONS OF THE GROUP OF DETECTING UNITS ON THE INDICATOR AT THE CENTRAL POST, WHEREBY, IN CASE OF ALARM, THE CONDITION OF OPERATION OF EACH FIRE DETECTING UNIT IS VISIBLE WHEN THE GRID ELECTRODE LIGHTS UP. 